The present invention relates to a method for the preparation of an emboss-worked plastic-made card or, more particularly, to a method for the preparation of an emboss-worked plastic-made card useful as a multi-functional IC card for operation of computers.
An IC card or a multi-functional IC card is constructed from a body of the card having a circuit board mounting a memory IC, liquid-crystal display unit, solar cell, lithium battery and the like built therein and provided with terminals for electric connection with an external electronic instrument and covering sheets bonded to the surfaces of the card body each with an interposed adhesive layer.
The IC card or a multi-functional IC card as compared with conventional computer-operating cards with a magnetic stripe is characteristic in the greatly increased capacity for information memory and is highlighted and expected to be widely employed as data files for office automation or factory automation, clinical charts in hospitals, pocketable personal memory banks, process-control cards and the like, some IC cards being already under practical use in these applications. In particular, multi-functional IC cards can be imparted with compatibility with and are replaceable with conventional existing bankcards for operating cash dispensers and the like when the IC card is provided with a magnetic stripe and an embossed relief pattern indicating letters and symbols as in the conventional computer-operating cards. The embossed relief on a computer-operating card has a dimensions specified in ISO 7810 and JIS X 6301. Namely, the body of an IC card has dimensions of 54.0 mm width, 85.6 mm length and 0.76 mm thickness and the embossed relief pattern formed in a specified area of the card is raised on the surface of the body by a height of 0.48 mm. The patterns of the embossed relief include letters of various characters, numerical figures and symbols, the kinds of which are specified in the above mentioned JIS or other authorized standards.
In these IC cards and multi-functional IC cards, the various electronic components such as printed circuit boards and the like are disposed sometimes over an area extending to the zone allotted to the embossed relief pattern specified in the standard. Therefore, a difficult problem arises in the embossing work that, different from conventional computer-operating plastic-made cards with a magnetic stripe, the embossing work of the card with embossing dies cannot be undertaken after the covering sheets have been bonded to the card body already having such electronic components build therein because of the danger that the electronic components may eventually be destroyed by the pressure under the embossing dies.
Accordingly, a conventional procedure for the preparation of and IC card having an embossed relief pattern on at least one surface is that the covering plastic sheet is emboss-worked beforehand prior to adhesive bonding to the card body. This adhesive bonding method of an embossed covering sheet to the card body is also not and easy matter due to the extremely small thickness of the sheet of 0.05 to 0.10 mm in order that the overall thickness of the IC card after bonding of the covering sheets should not exceed 1 mm or, in particular, 0.76 mm because the embossed relief pattern may be sometimes crushed and flattened by the pressure in the hot press for the adhesive bonding work.
With an object to solve the above mentioned problems, the inventors have previously proposed an improved method in Japanese Patent Kokai No. 63-151496, according to which a plastic sheet for covering of an IC card is provided beforehand with an embossed relief pattern and the recess or cavity formed on the back surface of the sheet is filled with a synthetic resin curable by heating or irradiation with ultraviolet light or electron beams followed by curing of the resin to reinforce the embossed pattern prior to adhesive bonding to the card body. This method is also practically not quite advantageous because the apparatus for the process cannot be compact enough with high costs and the emboss-worked covering sheet may sometimes be subject to deformation in the course of curing of the cavity-filling resin with heating to expose the surface of the sheet outside the resin-filled cavity to the radiant heat.
Alternatively, a method is proposed that flat covering sheets are adhesively bonded to the card body and then a strip of an additional sheet having an embossed relief pattern is bonded to the covering sheet at the specified position on the surface of the card. This method is also not practical because the apparatus cannot be compact and the emboss-worked attachment strip sometimes falls off the covering sheet unless the adhesive bonding strength therebetween is high enough.